There are many complex network devices in a telecommunication network, such as a router, a gateway, a switch, a firewall, and various servers. These network devices each support various network protocols to implement interworking between network elements. In these network devices, each device is a network element and includes a packet forwarding module and a control module for various protocols.
Such distributed deployment of the control module in the network element makes deployment and management of the network highly complex, and to modify or upgrade a control parameter, a network operator needs to perform an operation on each device separately.
To resolve a problem with deployment flexibility and manageability of the network element, a concept of software-defined networking (Software-Defined Network, SDN) is proposed in the industry.
In the SDN, control logic and a forwarding function of the network element are decoupled, and the control logic is centrally deployed, so that work of control and maintenance of the network can be implemented simply by operating a control plane device, thereby improving network management efficiency, simplifying a forwarding plane device, and helping achieve high performance and reusability of a forwarding device.
Currently, the SDN idea is being widely applied in a data center network and a telecommunication network. In an SDN network, the most typical and most frequently used protocol is the OpenFlow (Openflow) protocol.
A network element in the Openflow protocol includes an OpenFlow controller (openflow controller, OF Controller for short) and an OpenFlow switch (openflow switch, OF Switch for short).
The OF Controller is responsible for determining a forwarding action, for example, forwarding, discarding, packet header modification, encapsulation, or decapsulation, for the service flow according to packet features such as an IP (Internet Protocol, IP for short) 5-tuple, an Ethernet frame header, and a VLAN ID (Virtual Local Area Network IDentifier, VLAN ID for short), and delivering a corresponding flow entry to the OF Switch. The flow entry includes flow matching information such as an IP 5-tuple and an Ethernet frame header, and a corresponding executed action.
The OF Switch acquires and stores the flow entry, and executes a corresponding action on a subsequent packet conforming to the flow matching information.
When the OF Controller requires the OF Switch to send a packet to an external network element, the OF Controller sends a to-be-sent packet and a corresponding executed action to the OF Switch by using a packet sending message (Packet_Out).
Because the OF Controller uses an independent flow entry installation message Flow_mod and packet sending message Packet_Out, a relatively large quantity of messages are exchanged between the OF Controller and the OF Switch. Therefore, if a process is frequently executed, for example, handover is simultaneously performed for a large quantity of users, a great deal of signaling load is caused to control interfaces, and control interfaces in an entire system are in an overloaded state.